Engraving head support system with linear head driver

ABSTRACT

A platform for supporting an engraving head in a manner accommodating translational movement without any associated rotation. The platform has a deck which is supported by a pair of flexible support columns. In operation the platform is situated alongside a rotating printing cylinder. The engraving head is mounted on the deck of the platform and is provided with a guide shoe which rides against the surface of the printing cylinder. As the cylinder rotates to angular positions having different radii, the engraving head responds with a purely linear reaction. Consequently the engraving head is able to engrave uniform-depth cavities in the surface of the printing cylinder. In two alternative embodiments the deck is driven by a resilient link arrangement which is coupled to a leadscrew and carriage assembly.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of Ser. No. 08/091,302, filed Jul.12, 1993, now issued as U.S. Pat. No. 5,454,306.

BACKGROUND OF THE INVENTION

This invention relates to electronic engraving devices for engravingink-receiving cavities into the surface of a gravure printing cylinder.Such engraving devices commonly comprise an engraving head whichincludes a diamond stylus and a guide shoe. The guide shoe bears againstthe printing cylinder and provides a reference surface for the engravingprocess. An electromagnetic driver is mounted within the engraving headfor oscillating the stylus into engraving contact with the printingcylinder. Meanwhile the printing cylinder rotates about its cylindricalaxis. The engraving head is supported such that it moves parallel to theaxis of the printing cylinder in synchronism with printing cylinderrotation. A typical prior art device is shown in Buechler U.S. Pat. No.4,450,486.

A prior art device of the type disclosed in the Buechler patent supportsthe engraving head in a manner generally as illustrated in FIG. 1hereof. Thus an engraving head 12 supports a guide shoe 13 against aprint cylinder 10 which is rotating in the direction indicated by thearrow 11. Engraving head 12 rests upon a deck 16 which in turn issupported by a base 20. Base 20 is horizontally moveable as indicated bythe arrow 15, while deck 16 is rotatable about an axis 18. Rotation ofdeck 16 about axis 18 produces rotational movement of engraving head 12as indicated by the arrow 93. A diamond engraving stylus (notillustrated in FIG. 1) is mounted alongside guide shoe 13 and is broughtinto engraving contact against cylinder 10 by a combination oftranslational motion and rotary motion. During setup the rotationalposition angle of engraving head 12 is adjusted so as to align the guideshoe and engraving stylus to the cylinder surface and produce a desiredprinting cell depth for a predetermined stylus driving signal.Unfortunately the rotation of engraving head 12 changes the orientationof the stylus as well as its cutting depth. This produces unwantedengraving errors.

It is therefore seen that there is a need for engraving head supportmeans capable of positioning a stylus against a printing cylinder bytranslational motion only.

SUMMARY OF THE INVENTION

In an engraving apparatus according to the present invention anengraving head translates a stylus, without rotation, into engravingcontact with a rotating printing cylinder. The engraving head is mountedon a platform comprising a deck and a base joined by connection meanswhich permit the deck to move relative to the base only by translationwithin a plane perpendicular to the axis of the printing cylinder. Inone embodiment the connection means comprise a pair of parallel supportcolumns. The support columns may be deflected in parallel fashion toenable movement of the deck relative to the base. However, the deckremains parallel to the base at all times. The engraving head rests onthe deck and cannot rotate relative to the printing cylinder.

Preferably the support columns are secured fast to the deck and the baseand accommodate translation of the deck by parallel flexing. The flexingoccurs within a plane perpendicular to the axis of rotation of theprinting cylinder, and a parallel relation between the deck and the baseis maintained. The platform is so constructed as to prevent relativemovement between the deck and the base in a direction parallel to theaxis of the printing cylinder.

In alternate embodiments the connection means comprise a carriage drivenby a motor and a leadscrew which are mounted in the base. A resilientlink arrangement couples the carriage to the deck.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevation sketch of a prior art support arrangement foran engraving head.

FIG. 2 is a side elevation sketch of a support arrangement for anengraving head according to the present invention.

FIG. 3 is an enlarged view of a portion of FIG. 2.

FIG. 4 is a top plan view illustrating the geometrical relationshipbetween an engraving stylus and a guide shoe.

FIG. 4a is a schematic illustration of the engraving action of thepresent invention.

FIG. 4b is a schematic illustration of the engraving action whichresults when engraving head rotation is permitted to occur.

FIG. 5 is a perspective view of the upper end of a front support column.

FIG. 6 is a cross-sectioned side elevation view of a second embodimentof an engraving head support arrangement.

FIG. 7 is a cross-sectioned side elevation view of a third embodiment ofan engraving head support arrangement.

FIG. 8 is a perspective drawing of the support arrangement of FIG. 6.

FIG. 9 is a perspective drawing of the support arrangement of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A support platform 50 according to the present invention may beconfigured as illustrated generally in FIG. 2. Platform 50 supports anengraving head 12 for translational movement between a positionillustrated in solid lines and another position illustrated in dottedlines. A bias mechanism, such as a compression spring 26, urgesengraving head 12 toward a normal operating position wherein a guideshoe 13 is in surface-to-surface contact with printing cylinder 10. Asecond such compression spring may be installed at the remote end ofplatform 50. The movement is two-dimensional and parallel; no rotationbeing permitted. The plane of movement is perpendicular to the axis ofrotation 45 of printing cylinder 10. Referring now to FIG. 4, there isshown a top plan view of an engraving stylus 14 and a guide shoe 13.When guide shoe 13 is ideally positioned, as illustrated in FIG. 4, itcontacts printing cylinder 10 along a contact line 34. Cutting tip 98 ofstylus 14 cuts into printing cylinder 10 along an extension of contactline 34. The engraving action thereof is illustrated in FIG. 4a.

As shown in FIG. 4a, cutting tip 98 oscillates in the direction of thedouble headed arrow 17 so as to cut into the surface 30 of printingcylinder 10. Printing cylinder 10 moves in a direction as indicated bythe arrow 11, and the oscillating stylus cuts a channel indicated by theprofile 32.

During engraving the guide shoe 13 and stylus 14 may move radiallytoward and away from the axis of the printing cylinder 10 to accommodatefor runout due to the surface condition of the printing cylinder 10. Inthe embodiment being described, this radial movement is in the order ofabout 0-0.01 inch, but it could be less or greater if desired. A priorart arrangement as illustrated in FIG. 1, the distance between stylus 14and axis 18 may be in the order of about 6 inches. Therefore stylus 14rotates relative to cylinder 10 through an angle of about 1/2milliradian. This is illustrated in exaggerated form by the angle A ofFIG. 4b. Such rotation of stylus 14 causes an alteration of theengraving action. Thus, stylus 14 may engrave cavities as illustrated bythe phantom line 32a whereas cavities 32 are desired.

Platform 50 comprises a deck 15 supported upon a base 24 by a frontsupport column 22a and a rear support column 22b. Preferably the supportcolumns are secured fast to the deck 20 and base 24 at fixed points ofattachment. Support columns 22a and 22b are of matching construction andmay be flexed to accommodate parallel motion of engraving head 12. Inthe unstressed or rest position, columns 22a and 22b extendperpendicularly between deck 15 and base 24. Base 24 is connected to asuitable driving mechanism (not illustrated) operative in the directionindicated by the double arrows 25 for driving platform 50 from a restposition to an operating position shown in solid lines in FIG. 2. Acompression spring 26 maintains guide shoe 13 in contact with printingcylinder 10 during normal operation. Thereafter guide shoe 13 maintainscontact with the surface of cylinder 10 by linear movement only (asshown in exaggerated form by the dotted lines in FIG. 2).

FIG. 3 illustrates front support column 22a in more detail. In theillustrated embodiment, support column 22a comprises a beam 40, an upperleaf spring 42 and a lower leaf spring 44. Upper leaf spring 42 may befabricated from spring steel and joins deck 15 to beam 40. Lower leafspring 44 is likewise of spring steel construction and joins beam 40 tobase 24. Beam 40 may be a rigid member, if desired. Alternatively, beam40 and leaf springs 42,44 could be replaced by a single leaf spring.During translation of deck 15, leaf springs 42,44 are flexed asindicated by the dotted lines in FIG. 3.

FIG. 5 illustrates the front upper leaf spring 42 in perspective. Itwill be seen that leaf springs 42,44 and beam 40 extend a substantialdistance in a direction parallel to cylinder axis 45 so as to inhibitflexing of support columns 22a, 22b in that direction. It will beunderstood, however, that base 24 is attached to a carriage (notillustrated) which is driven in a controlled manner in a directionparallel to the axis 45. It is desired that motion of stylus 14 in thedirection of the cylinder axis be restricted to that which is impartedby a carriage 27 (FIG. 2) on which the base 24 is mounted.

A second embodiment of the invention may be constructed as generallyillustrated in FIGS. 6 and 8. In this embodiment the engraving head 12is supported by a platform 150 having a base 124 in the form of a trackchannel. A leadscrew 108 is mounted in base 124 and is driven by a motor110. A carriage 102 is threadably engaged by leadscrew 108 forhorizontal movement in response to rotation of motor 110. Carriage 102supports a guideway 104 having end walls 132 and 134. Engraving head 12rests upon a deck 115 supported within guideway 104. A pair ofcompression springs 106,107 are compressed between deck 115 and endwalls 132,134 respectively of guideway 104. As illustrated in FIG. 8, apair of fingers 112,114 are mounted on a side wall of guideway 104 andare sensed by a proximity sensor 116 supported on deck 115.

The embodiment of FIGS. 6 and 8 is set up by operating motor 110 to moveengraving head 12 in a direction toward printing cylinder 10. When guideshoe 13 comes into engagement against the surface of printing cylinder10, compression spring 106 begins compressing, and fingers 112,114 beginmoving relative to proximity sensor 116. Proximity sensor 116 isconnected to terminate power to motor 110 when a predetermined movementof fingers 112,114 has been sensed. This causes guide shoe 13 to rideagainst printing cylinder 10 with a predetermined contact force. Thecontact force is a function of the spring constants of compressionsprings 106,107. Preferably, one of springs 106,107 has a stiffnessslightly greater than the other, so that a finite contact force ismaintained. Preferably, base 124 incorporates bearing tracks (notillustrated) for providing guided linear movement of carriage 102. Inthe embodiment being described, the bearing tracks may be conventionallinear bearing tracks.

A third embodiment of the invention is illustrated in FIGS. 7 and 9. Theembodiment of those figures is similar to the embodiment of FIGS. 6 and8 in that it employs a base 124 fitted with a leadscrew 108 driven by amotor 110. A carriage 202 is threadably engaged by leadscrew 108.Carriage 202 drives an upstanding arm 213 which extends upwardly into anopening 211 in deck 204. Deck 204 is mounted on a table 205 whichreceives, but does not engage, leadscrew 108. Carriage 202 and table 205may have bearings 264,266 respectively which ride within a track 260 inbase 124. A second track and other bearings (not illustrated) may beprovided opposite track 260 and bearings 264,266.

Deck 204 supports engraving head 12 and is driven by forces exerted upona pair of compression springs 206,207 by arm 213. Arm 213 is upwardlyterminated by a pair of fingers 212,214 which are sensed by a proximitysensor 216. Proximity sensor 216 is supported by deck 204 so as to senserelative movement of fingers 212,214 which occurs during setup whenguide shoe 13 comes into contact with the surface of printing cylinder10. As with the previously discussed embodiment, a predeterminedrelative movement of fingers 212,214 causes proximity sensor 216 todisconnect power from motor 110. Again, guide shoe 13 rests against thesurface of cylinder 10 with a predetermined force.

An engraving head platform according to the present invention eliminatesthe prior art head pivoting mechanism while improving engravingaccuracy. Advantageously, the guide shoe may be brought into directcontact with a rotating printing cylinder without any need for manualsetup.

While the form of apparatus herein described constitute preferredembodiments of this invention, it is to be understood that the inventionis not limited to these precise forms of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:
 1. A support for use in an engraving system whichmoves an engraving stylus into surface contact with a printing cylinderrotating about a cylindrical axis thereof, and an engraving head forsupporting said stylus; said support comprising:a deck for supportingsaid engraving head, a base extending parallel to said deck, and aconnector for connecting said deck and said base such that said deck maymove relative to said base only by translation within a planeperpendicular to said cylindrical axis; said engraving system comprisinga driver for driving said support towards and away from the printingcylinder.
 2. The support of claim 1 wherein said connector comprises:aleadscrew supported by said base and having a leadscrew axis situatedwithin said plane, a motor for rotating said leadscrew, a carriagejoined to said leadscrew for bi-directional movement parallel to saidleadscrew axis in response to rotation of said leadscrew, and a couplingbetween said carriage and said deck.
 3. An engraving head support forsupporting an engraving head having a stylus against a surface of acylinder while said cylinder rotates about a cylindrical axis thereof;said engraving head support comprising:a deck for supporting saidengraving head in a plane substantially parallel to said cylindricalaxis, a base extending parallel to said deck and spaced apart therefromon the side thereof which is remote from said engraving head, and aplurality of flexible support columns extending between said deck andsaid base and mounted fast thereto for accommodating radial movement ofsaid deck, said engraving head and said stylus toward said cylinder. 4.The engraving head support according to claim 3 wherein said pluralityof flexible support columns comprise parallel front and rear supportcolumns extending in a direction parallel to said cylindrical axis whilesubstantially inhibiting flexure thereof in the direction of saidcylindrical axis.
 5. The engraving head support according to claim 4wherein said front and rear support columns are of matchingconstruction, each comprising a relatively rigid beam, an upper leafspring joining said beam to said deck and a lower leaf spring joiningsaid beam to said base.
 6. A support platform for an engraving headcomprising:a deck for supporting said engraving head, a base extendingparallel to said deck, and a pair of matching support columns mountedfast between said deck to said base; said support columns being flexiblein a predetermined plane perpendicular to said base and said base andbeing relatively inflexible in a direction which is perpendicular tosaid plane.
 7. A support platform for an engraving head comprising:abase; a leadscrew associated with said base; a motor for rotating saidleadscrew; a carriage coupled to said leadscrew for linear movement inresponse to rotation of said leadscrew; a deck for supporting saidengraving head; spring means interconnecting said carriage and saiddeck, so that said deck and said engraving head flexibly follow themovement of said carriage and flexibly react to a force applied to saidengraving head by a workpiece; and guide means for guiding said deck andsaid engraving head along a straight line during flexible reactingthereof.
 8. The support platform according to claim 7 further comprisingsensing means operative during setup of said engraving head for sensingflexible reaction of said engraving head and responding thereto byde-energizing said motor.
 9. The support platform according to claim 7wherein said guide means comprises a guideway provided with a guidechannel and mounted to said carriage, said deck being slidably receivedwithin said guide channel, and said spring means being mounted withinsaid guide channel in contact with said deck.
 10. The support platformaccording to claim 7 wherein said guide means are slidably mountedwithin said base and said deck is mounted fast to said guide means. 11.The support platform according to claim 7 further comprising an armsecured to said carriage, said deck being provided with an opening forreceiving said arm, and said spring means being mounted in said openingin contact with said arm.
 12. The support platform according to claim 11wherein said spring means comprises a pair of compression springspositioned in contact with opposite sides of said arm.
 13. The supportplatform according to claim 7 wherein said guide means moves radiallytoward and away from the axis of the printing cylinder to accommodatefor runout.
 14. The support platform according to claim 13, wherein saidmovement is on the order of 0-0.010 inch.
 15. An engraving head supportsystem comprising:a carriage for supporting an engraving head comprisinga stylus for engraving a cylinder as the carriage moves in a directionparallel to an axis of a surface of said cylinder; and a driver coupledto said carriage for permitting said engraving head to be drivenradially in a direction which is substantially perpendicular to an axisof rotation of said cylinder.
 16. The engraving head support system asrecited in claim 15 wherein said support comprises a deck for supportingsaid engraving head, a platform and at least one column for flexiblycoupling said deck to said platform.
 17. The engraving head supportsystem as recited in claim 16 wherein said at least one support columncomprises spring steel.
 18. The engraving head support system as recitedin claim 15 wherein said flexible support comprises a plurality ofsupport columns.
 19. The engraving head support system as recited inclaim 18 wherein said plurality of support columns are each springsteel.
 20. The engraving head support system as recited in claim 18wherein at least one of said plurality of support columns comprises astiffness which is greater than another of said plurality of supportcolumns.
 21. The engraving head support system as recited in claim 15,further comprising a sensor associated with said carriage for sensingwhen said engraving head contacts said surface of said cylinder.
 22. Theengraving head support system as recited in claim 21 wherein said sensoris mounted on said carriage.
 23. An engraver comprising:a carriagesituated on said engraver; an engraving head situated on said carriagefor engraving a cylinder as the carriage moves in a direction parallelto an axis of a surface of said cylinder; and a driver coupled to saidcarriage for permitting said engraving head to be driven in a lineardirection towards and away from said cylinder.
 24. The engraver asrecited in claim 23 wherein said engraver comprises a deck forsupporting said engraving head, a platform and at least one column forflexibly coupling said deck to said platform.
 25. The engraver asrecited in claim 24 wherein said at least one support column comprisesspring steel.
 26. The engraver as recited in claim 23 wherein saidflexible support comprises a plurality of support columns.
 27. Theengraver as recited in claim 26 wherein said plurality of supportcolumns are each spring steel.
 28. The engraver as recited in claim 26wherein at least one of said plurality of support columns comprises astiffness which is greater than another of said plurality of supportcolumns.
 29. The engraver as recited in claim 23, further comprising asensor associated with said carriage for sensing when said engravinghead contacts said surface of said cylinder.
 30. The engraver as recitedin claim 29 wherein said sensor is mounted on said carriage.
 31. Theengraver as recited in claim 23 wherein said engraving head comprises ashoe; said driver driving said carriage until said shoe engages saidcylinder with a predetermined force.
 32. The engraver as recited inclaim 23 wherein said engraving head comprises a shoe; and said driverbrings said shoe into contact with said cylinder during rotation of thecylinder.